The aims of this project are (1) to compare the locations of PGHS-1 and PGHS-2 within the nuclear envelope of murine 3T3 cells by fractionation of nuclear membranes and by immunoelectron microscopy, (2) to determine using an histofluorescence assay for PGHS activity the subcellular site of action of PGHS-2 when this enzyme utilizes arachidonic acid mobilized from endogenous phospholipid, (3) to determine by nuclear membrane fractionation and immunoelectron microscopy of thromboxane A synthase is on the nucleoplasmic surface of retinoic acid-activated HL60 cells, (4) to determine by nuclear membrane fractionation and immunoelectron microscopy of prostacyclin synthase is on the nucleoplasmic surface of PMA-activated human umbilical vein endothelial cells, (5) to identify the structural domain responsible for concentrating PGHS-2 in the nuclear envelope, and (6) to identify the structural domain responsible for targeting PGHS-1 to the endoplasmic reticulum.